In males, testosterone (T) levels decline with ageing. Several symptoms characteristic of the ageing process are similar to those related to hypogonadism. The aim of the present study was to evaluate the specific association among hypogonadism-related symptoms and signs and the ageing process. A consecutive series of 1647 (mean age 52.4 ± 13.1 years) male patients with sexual dysfunction were investigated. Several hormonal and biochemical, instrumental and psychological parameters were studied. The parameters significantly associated with total levels in the entire cohort, after adjustment for confounders, were studied as a function of age and T quartiles. In all age quartiles, low T was associated with higher waist circumference and triglyceride levels and with an increased prevalence of metabolic syndrome. The prevalence of hypoactive sexual desire decreased as a function of T only in the youngest (17- to 42-year old) age quartile as well as the reported reduction in nocturnal erections. In the oldest age quartile, we found an inverse relationship between T levels and the prevalence of severe erectile dysfunction and a positive relationship with intercourse frequency. Accordingly, in the oldest age quartile, subjects with higher T levels showed better penile flow at penile colour doppler ultrasound as well as a better lipid profile. Finally, an inverse association between somatized anxiety and T levels was observed only in the oldest age quartile. In conclusion, our study shows for the first time that in subjects with sexual dysfunction, some hypogonadism-related symptoms can be age-specific. In particular, low T is associated with sexual dysfunction more often in the oldest subjects.